In a packet switched communication system such as a router, a switch or other appropriate networking devices, there is often a need to exchange data between the network and the switch fabric of the system. Typically, data received from the network is buffered in a number of queues. A queue scheduler determines the order in which the queues are to be serviced. Data in a queue scheduled to be serviced are sent to one or more links associated with a switch fabric. In some cases, the queue scheduler uses a round robin (RR) scheme that gives each of the queues equal opportunity to be serviced. In some cases, in order to control the quality of service (QOS) and groom traffic, the queue scheduler uses a weighted round robin (WRR) scheme that services the queues with different priority levels.
Although the weighted round robin scheduler offers good grooming of the source traffic when the switch fabric receiving the traffic data has no congestion, problems may arise when the switch fabric experiences congestion. Upon detecting heavy traffic on any of its links, the switch fabric sends back congestion signals indicating that traffic to the congested links should be reduced. The queue scheduler typically reduces traffic by not servicing the queues associated with the congested links; however, this may cause queue starvation and interruption of the expected grooming. As a result, the service quality of time sensitive applications such as audio/video streaming and voice over IP may be degraded. It would be desirable to have a technique that would prevent the queue starvation problem and ameliorate the interruption to traffic grooming when there is high volume of traffic on one or more links.